#include<iostream>
using namespace std;
#include<vector>
class Solution {
public:
    int minDistance(string word1, string word2) {
        int m = word1.size(), n = word2.size();
        word1 = ' ' + word1;
        word2 = ' ' + word2;
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));
        for (int i = 0; i <= m; ++i)
            dp[i][0] = i;
        for (int i = 0; i <= n; ++i)
            dp[0][i] = i;
        for (int i = 1; i <= m; ++i) {
            for (int j = 1; j <= n; ++j) {
                if (word1[i] == word2[j])
                    dp[i][j] = dp[i - 1][j - 1];
                else
                    dp[i][j] = min(dp[i][j - 1], min(dp[i - 1][j], dp[i - 1][j - 1])) + 1;
            }
        }
        return dp[m][n];
    }
};